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copied!<p>There is a fantastic package in Python called <a href="http://docs.python.org/library/itertools.html" rel="noreferrer"><code>itertools</code></a>.</p> <p>But before I get into that, it'd serve well to explain how the iteration protocol is implemented in Python. When you want to provide iteration over your container, you specify the <a href="http://docs.python.org/reference/datamodel.html#object.__iter__" rel="noreferrer"><code>__iter__()</code></a> class method that provides an <a href="http://docs.python.org/library/stdtypes.html#iterator-types" rel="noreferrer">iterator type</a>. <a href="http://effbot.org/zone/python-for-statement.htm" rel="noreferrer">"Understanding Python's 'for' statement"</a> is a nice article covering how the <code>for-in</code> statement actually works in Python and provides a nice overview on how the iterator types work.</p> <p>Take a look at the following:</p> <pre><code>>>> sequence = [1, 2, 3, 4, 5] >>> iterator = sequence.__iter__() >>> iterator.next() 1 >>> iterator.next() 2 >>> for number in iterator: print number 3 4 5 </code></pre> <p>Now back to <code>itertools</code>. The package contains functions for various iteration purposes. If you ever need to do special sequencing, this is the first place to look into.</p> <p>At the bottom you can find the <a href="http://docs.python.org/library/itertools.html#recipes" rel="noreferrer">Recipes</a> section that contain <em>recipes for creating an extended toolset using the existing itertools as building blocks</em>.</p> <p>And there's an interesting function that does exactly what you need:</p> <pre><code>def consume(iterator, n): '''Advance the iterator n-steps ahead. If n is none, consume entirely.''' collections.deque(itertools.islice(iterator, n), maxlen=0) </code></pre> <p>Here's a quick, readable, example on how it works <em>(Python 2.5)</em>:</p> <pre><code>>>> import itertools, collections >>> def consume(iterator, n): collections.deque(itertools.islice(iterator, n)) >>> iterator = range(1, 16).__iter__() >>> for number in iterator: if (number == 5): # Disregard 6, 7, 8, 9 (5 doesn't get printed just as well) consume(iterator, 4) else: print number 1 2 3 4 10 11 12 13 14 15 </code></pre>

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